Vietnam's benchmark VN Index rose 0.33 percent by the midday break on Friday on low volume, but activity from exchange-traded funds' (ETF) could boost liquidity in the afternoon session, an analyst said.

Volume was at 34 million shares by midday, well below the five-day average level of 90 million, Reuters data showed.

"Most activities on the market this morning were of the ETFs on their last trading day of the second-quarter portfolio restructuring," said Nguyen Hoang Phuong, an analyst with Ho Chi Minh City Securities.

The Market Vectors Vietnam and db x-trackers FTSE Vietnam ETFs will finalise their portfolio restructuring on Friday, which will boost volume on the exchange in the afternoon session, Phuong added.